CN114093253A

CN114093253A - Foldable window of display device

Info

Publication number: CN114093253A
Application number: CN202110973879.8A
Authority: CN
Inventors: 张硕元; 郑哲豪; 具达索; 全勇灿
Original assignee: Samsung Display Co Ltd
Current assignee: Samsung Display Co Ltd
Priority date: 2020-08-24
Filing date: 2021-08-24
Publication date: 2022-02-25
Also published as: US11740655B2; US20220057834A1; KR20220025969A

Abstract

The present disclosure relates to a foldable window of a display device, the foldable window comprising: a first film having a modulus; a second film facing the first film, closer to a display panel of the display device than the first film, and having a modulus; and an adhesive layer between the first film and the second film, joining the first film to the second film, wherein the modulus of the first film and the modulus of the second film are both equal to or greater than 7 gigapascals.

Description

Foldable window of display device

This application claims priority and benefit from korean patent application No. 10-2020-0105947, filed 24/8/2020, which is incorporated herein by reference in its entirety.

Technical Field

The present disclosure herein relates to a foldable window and a display device including the same. More particularly, the present disclosure relates to a foldable window having improved durability and impact resistance and a display device including the same.

Background

The display device provides information to a user by displaying various images on a display screen. Typically, the display device displays information within an assigned display screen. The display apparatus may be used to display images on various electronic devices such as smart phones, notebook computers, and televisions.

Flexible display devices have been developed that include a foldable flexible display panel. Unlike rigid display devices, flexible display devices may be foldable, rollable, or bendable. The flexible display device variously changeable in shape can be conveniently transported to improve user convenience.

Disclosure of Invention

The present disclosure provides a foldable window of a display device having improved durability and impact resistance and a display device including the same.

Embodiments provide a foldable window, comprising: a first film having a modulus; a second film facing the first film, closer to a display panel of the display device than the first film, and having a modulus; and an adhesive layer between the first film and the second film, bonding the first film to the second film. The modulus of the first film and the modulus of the second film are both equal to or greater than about 7 gigapascals (GPa).

In an embodiment, each of the first and second films may include a polyimide copolymer, a polyamide copolymer, or a polyimide-polyamide copolymer.

In an embodiment, each of the thickness of the first film and the thickness of the second film may be equal to or greater than about 10 micrometers (μm) and equal to or less than about 35 micrometers (μm).

In an embodiment, each of the modulus of the first film and the modulus of the second film may be equal to or greater than about 7GPa and equal to or less than about 15 GPa.

In an embodiment, the adhesive layer may have a thickness equal to or greater than about 1 micrometer (μm) and equal to or less than about 5 micrometers (μm).

In an embodiment, the adhesive layer has an adhesive strength that forms an interface with both the first film and the second film, and the adhesive strength of the adhesive layer may be equal to or greater than about 7 newtons per 20 millimeters (N/20 mm).

In an embodiment, the adhesive layer may include an epoxy-based resin or a urethane acrylate-based resin.

In an embodiment, the first film and the second film may comprise the same material.

In an embodiment, the foldable window may further comprise a third film on the first film or the second film, and the modulus of the third film may be equal to or greater than about 7 GPa.

In an embodiment, the foldable window may further comprise a hard coating layer on the first film to define an impact resistant layer.

In an embodiment, the hard coating layer may include a water or oil repellent substance (e.g., material).

In an embodiment, the foldable window may further include an inorganic layer, which may contact at least one surface of the first film or the second film and be separated from the adhesive layer.

In an embodiment, the inorganic layer may have a thickness equal to or greater than about 5 angstroms

And equal to or less than about 500

In an embodiment, the foldable window may have a moisture vapor transmission rate equal to or greater than about 0.01 grams per square meter per day (g/m)²Days) and equal to or less than about 10 grams per square meter per day (g/m)²·day)。

Another embodiment provides a display apparatus including a foldable display module and a foldable window facing and foldable with the display module. The foldable window includes a plurality of films and at least one adhesive layer joining the plurality of films to each other. The adhesive layer has an adhesive strength of about 7N/20mm or more, and a thickness of about 5 μm or less.

In an embodiment, the thickness of the foldable window may be about 40 μm to about 100 μm.

In an embodiment, each of the moduli of the plurality of films may be about 7GPa to about 15 GPa.

In an embodiment, each of the plurality of films may include a polyimide copolymer, a polyamide copolymer, or a polyimide-polyamide copolymer.

In an embodiment, the foldable window may further include a hard coating layer (i.e., an impact resistant layer) as an uppermost film of the plurality of films, and the hard coating film may include a water-or oil-repellent substance.

In an embodiment, the foldable window may further include an inorganic layer in contact with at least one of an upper surface of an uppermost film of the plurality of films and a lower surface of a lowermost film of the plurality of films.

The inorganic layer may have a thickness of about

To about

Drawings

The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the invention. In the drawings:

FIG. 1 is a perspective view of an embodiment of a display device;

FIG. 2A is a perspective view illustrating the display device shown in FIG. 1 folded;

FIG. 2B is a perspective view illustrating the display device shown in FIG. 1 folded;

FIG. 2C is a perspective view illustrating the display device shown in FIG. 1 folded;

FIG. 2D is a perspective view illustrating the display device shown in FIG. 1 folded;

FIG. 3 is an exploded perspective view of an embodiment of a display device;

FIG. 4 is a cross-sectional view of an embodiment of a collapsible window;

FIG. 5 is a cross-sectional view showing an embodiment of a pen drop test for a collapsible window;

FIG. 6 is a sectional view illustrating an embodiment of a process of measuring a deformation angle of a foldable window;

FIG. 7 is a sectional view illustrating an embodiment of a process of measuring a deformation angle of a foldable window;

FIG. 8 illustrates an embodiment of a stress-strain graph of a film of a foldable window;

FIG. 9 is a sectional view showing an embodiment of the foldable window of FIG. 3;

FIG. 10 is a sectional view showing an embodiment of the foldable window of FIG. 3;

FIG. 11 is a sectional view showing an embodiment of the foldable window of FIG. 3;

FIG. 12 is a sectional view showing an embodiment of the foldable window of FIG. 3; and

FIG. 13 is a cross-sectional view of an embodiment of a display module.

Detailed Description

In the present invention, various changes and modifications can be made and various forms can be applied, and embodiments are shown in the drawings and will be described in detail in this specification. However, the present invention should not be limited to these embodiments, and it is to be understood that all changes, modifications, equivalents, and substitutions included in the spirit and scope of the present invention are to be included therein.

It will be understood that when an element (region, layer or section, etc.) is referred to as being "on," "connected to" or "coupled to" another element, it can be directly on, connected or coupled to the other element or intervening elements may be present. In contrast, when an element (region, layer or section, etc.) is referred to as being associated with another element, e.g., "directly on," "directly connected to" or "directly coupled to" another element, there are no intervening elements present.

Like reference numerals refer to like elements throughout. Thicknesses and proportions of elements, as well as dimensions, have been exaggerated in order to effectively describe the technical contents.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the terms "a", "an", "the" and "at least one" do not denote a limitation of quantity, but rather are intended to encompass both the singular and the plural, unless the context clearly dictates otherwise. For example, "an element" has the same meaning as "at least one element" unless the context clearly dictates otherwise. "at least one" should not be interpreted as a limiting "of one" or "one". "or" means "and/or". As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present invention. Similarly, a second element, component, region, layer or section could be termed a first element, component, region, layer or section.

Furthermore, spatially relative terms, such as "below," "lower," "above," and "upper," may be used herein to facilitate describing one element or feature's relationship to another element or feature as illustrated. Terms used herein are relative concepts and are described based on directions in the drawings.

"about" or "approximately" as used herein includes the recited value, given the measurement in question and the error associated with measurement of the particular quantity (i.e., the limitations of the measurement system), and is intended to mean within an acceptable range of deviation of the particular value as determined by one of ordinary skill in the art. For example, "about" can mean within one or more standard deviations, or within ± 30%, ± 20%, ± 10% or ± 5% of the recited values.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

It will be further understood that the terms "comprises," "comprising," "includes" and/or "including," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, components, and/or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

Embodiments are described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, the embodiments described herein should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, a region shown or described as flat may generally have rough and/or nonlinear features. Furthermore, the acute angles shown may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region and are not intended to limit the scope of the claims.

The flexible display device, which can be variously changed in shape, can be easily carried to improve convenience to a user. However, the foldable flexible display device has a limitation of being vulnerable to external impact.

Hereinafter, embodiments of the foldable window WM and the display device DD including the same will be described in detail with reference to the accompanying drawings.

Fig. 1 is a perspective view of an embodiment of a display device DD. Fig. 2A to 2D are perspective views illustrating an embodiment of the display device DD shown in fig. 1 folded.

Referring to fig. 1, the display device DD has a rectangular shape having a short side extending along a first direction DR1 and a long side extending along a second direction DR2 crossing the first direction DR 1. However, the shape of the display device DD is not limited thereto, and various shapes of the display device DD may be provided.

As shown in fig. 1, the front surface of the display device DD may be defined as a display surface IS. The display surface IS may be on a plane parallel to a plane defined by the first direction DR1 and the second direction DR2 crossing each other. The display surface IS may display the image IM in a third direction DR3 intersecting each of the first direction DR1 and the second direction DR 2. The third direction DR3 may define a thickness direction of the display device DD and its various components.

The upper surface (or front surface) and the lower surface (or rear surface) of each member are defined based on the direction in which the image IM is displayed. The upper and lower surfaces may face each other along the third direction DR3, and a normal direction of each of the upper and lower surfaces may be parallel to the third direction DR 3.

The directions indicated by the first direction DR1, the second direction DR2, and the third direction DR3 are relative concepts, and thus may be changed to other directions. Hereinafter, the above-described first to third directions are indicated by the first direction DR1, the second direction DR2, and the third direction DR3, respectively, and are denoted by like reference numerals.

The display surface IS of the display device DD may have a display area DA and a non-display area NDA defined therein. The display area DA may be an area or a planar area where the image IM is displayed, and the image IM may be visually recognizable from the outside of the display device DD at the display area DA. The image IM may be a moving image or a still image. As an example of the image IM, fig. 1, 2B, and 2D show a plurality of application icons. Various components or members of the display device DD may include a display area DA and a non-display area NDA corresponding to the display area DA and the non-display area NDA described above for the display device DD.

The display area DA may have a rectangular shape in plan view (e.g., along the third direction DR 3). The non-display area NDA is adjacent to the display area DA. The non-display area NDA may surround the display area DA. However, this is illustrated as an example, and the non-display area NDA may be disposed adjacent to only one side of the display area DA, or may be omitted. The display device DD may include various embodiments, and is not limited to one embodiment.

One or more embodiments of the display device DD may be not only a large-sized display device such as a television set or a display monitor, but also a small-sized or medium-sized display device such as a mobile phone, a tablet computer, a vehicle navigation unit, a game machine, or the like. These are provided as examples only. Accordingly, the display device DD may not be limited to any one embodiment.

The display device DD may sense an external input TC applied from the outside of the display device DD. The external input TC includes various types of input such as light, heat, or pressure, and may be applied through various input tools such as a body part, a pen, or the like. In fig. 1, a body part is shown as an external input TC applied to the front surface of the display device DD. However, this is illustrated as an example, and the external input TC may be provided in various types as described above. In addition, the display device DD may also sense an external input TC applied to a side surface or a rear surface of the display device DD according to the structure of the display device DD, and is not limited to any one embodiment.

The display device DD may activate the display surface IS to display the image IM and also to sense external inputs TC. In the embodiment, an area or a planar area where the external input TC is sensed is shown as being provided in the display area DA where the image IM is displayed. However, this IS illustrated as an example, and the region sensing the external input TC may be provided in the non-display region NDA or all regions of the display surface IS.

The display device DD may be a foldable display device. The display device DD is foldable or bendable about folding axes FX extending in certain directions, respectively.

The folding axis FX may extend in one of the first direction DR1 or the second direction DR2, respectively. In an embodiment, a folding axis FX extending along the first direction DR1 is defined as a first folding axis FX1, and a folding axis FX extending along the second direction DR2 is defined as a second folding axis FX 2. The folding axis FX may extend along or parallel to the long and/or short sides of the display device DD. The display device DD may be foldable about either or both folding axes FX.

The display device DD may have a plurality of regions defined therein according to the type of operation. The plurality of regions may be divided into a plurality of folding regions and a plurality of non-folding regions. The fold region may be defined between two non-fold regions.

The folding area is an area or a planar area where the display device DD is foldable about one or more folding axes FX and the curvature of the display device DD is defined by its folding. The non-folded regions may be respectively adjacent to opposite sides of the folded region. The non-folding region may be a region or a planar region where the display device DD is not foldable or remains flat even when the display device DD is folded about its folding axis FX.

Referring to fig. 1 in conjunction with fig. 2A and 2B, in a direction along the display surface IS, the first non-folding region NFA1 may be adjacent to a first side of the first folding region FA1 along the second direction DR2, and the second non-folding region NFA2 may be adjacent to a second side of the first folding region FA1 along the second direction DR2, wherein the second side IS opposite to the first side along the second direction DR 2.

As shown in fig. 2C and 2D, the third non-folded region NFA3 may be adjacent to a first side of the second folded region FA2 along the first direction DR1, and the fourth non-folded region NFA4 may be adjacent to a second side of the second folded region FA2 along the first direction DR1, wherein the second side is opposite to the first side along the first direction DR 1.

The display device DD may be inwardly foldable and/or outwardly foldable. The inward folding IS defined as a folding of the display device DD such that portions and non-folded regions of the display surface IS may face each other, and the outward folding IS defined as a folding of the display device DD such that portions and non-folded regions of the display surface IS may face outward (e.g., face outward of the display device DD). That is, the outwardly folded display device DD includes the rear surfaces of the folded display device DD such that portions of the rear surfaces face each other.

The display devices DD may both be inwardly foldable and outwardly foldable, or may be only one of inwardly foldable and outwardly foldable. The various components or members of the display device DD may be foldable with respect to each other.

Fig. 2A illustrates the display device DD shown in fig. 1 folded inward along a first folding axis FX1, and fig. 2B illustrates the display device DD shown in fig. 1 folded outward along a first folding axis FX 1. Fig. 2C illustrates the display device DD shown in fig. 1 folded inward along the second folding axis FX2, and fig. 2D illustrates the display device DD shown in fig. 1 folded outward along the second folding axis FX 2.

Referring to fig. 2A and 2C, the display device DD may be inwardly foldable by bending such that portions of a front surface of the display device DD face each other with respect to a folding axis FX. Accordingly, the display surface IS of the folded-in display device DD may be protected from elements or the environment outside the display device DD.

Referring to fig. 2B and 2D, the display device DD may be foldable outward by bending such that portions of a rear surface of the display device DD face each other with respect to a folding axis FX. When the portion of the display surface IS at the non-folding region IS exposed to the outside of the display device DD, the display device DD may display the image IM to the outside of the display device DD. The portion of the display surface IS at the fold area exposed to the outside of the display device DD may also display the image IM.

Each of the plurality of non-folding areas and folding areas may display an image providing a plurality of pieces of information independently of each other, or may display a plurality of portions of the image collectively providing a single piece of information, respectively.

In the embodiment, one folding area is defined in the display device DD, but the present invention is not limited thereto. According to an embodiment, the display device DD may have a plurality of folding areas defined therein.

Fig. 3 is an exploded perspective view of an embodiment of a display device DD. The display device DD may include a support part SP (e.g., a supporter), a display module DM, an anti-reflection layer RPL, and a foldable window WM, which are sequentially stacked along a third direction DR 3. That is, the support part SP, the display module DM, the anti-reflection layer RPL, and the foldable window WM are arranged along the third direction DR 3.

The display module DM may include a display panel DP and an input sensing unit ISP (e.g., an input sensing layer). The input sensing unit ISP may be disposed on the display panel DP to be closer to the foldable window WM than the display panel DP. The display module DM may generate and/or display an image IM according to the electrical signal and may transmit/receive information according to the external input TC.

The display panel DP may be a light emitting display panel, but is not particularly limited thereto. In an embodiment, the display panel DP may be an organic light emitting display panel or a quantum dot light emitting display panel, for example. The light emitting layer of the organic light emitting display panel may include an organic light emitting material. The light emitting layer of the quantum dot light emitting display panel may include quantum dots, quantum rods, and the like.

The input sensing unit ISP may be disposed or formed on the display panel DP, for example, by a continuous process so as to be directly disposed on the display panel DP, however, the present invention is not limited thereto. As an intermediate member, an adhesive film may be disposed between the input sensing unit ISP and the display panel DP to bond the input sensing unit ISP to the display panel DP. In the case where the input sensing unit ISP and the display panel DP are combined with each other through an intermediate member, the display panel DP and the input sensing unit ISP may be separately provided through separate processes, respectively, and then, the input sensing unit ISP may be fixed to the display panel DP through an adhesive film.

The display module DM may have an active area AA and a peripheral area NAA defined therein. The active area AA may be defined as an area or a plane area displaying the image IM provided from the display module DM. The display panel DP may generate an image IM and the input sensing unit ISP may sense information based on an external input TC provided to the display device DD.

The peripheral area NAA is adjacent to the active area AA. In an embodiment, for example, the peripheral area NAA may surround the active area AA. However, this is shown as an example, and the peripheral area NAA may be defined in various shapes, and is not limited to any one embodiment. According to an embodiment, the active area AA of the display module DM may correspond to at least a portion of the display area DA, and the peripheral area NAA of the display module DM may correspond to at least a portion of the non-display area NDA.

The foldable window WM may be disposed on the display module DM. The foldable window WM may comprise an optically transparent insulating material. Thus, the image IM generated from the display module DM passes through the foldable window WM and can be visually recognized from the outside of the display device DD. The foldable window WM may define an outer surface (or front surface) of the display device DD, but is not limited thereto.

The foldable window WM may be foldable about a first folding axis FX 1. That is, when the shape of the display module DM is changed, the shape of the foldable window WM may be changed accordingly. The foldable window WM may be foldable together with the display module DM.

The foldable window WM allows images IM from the display module DM to pass through the foldable window WM and be visible from outside the display device DD. The foldable window WM also reduces or effectively prevents malfunction or damage to the display module DM due to external impact by alleviating pressure or force applied to the display device DD due to the external impact.

The foldable window WM may have a multi-layered structure. The foldable window WM may include a plurality of films combined with each other by at least one adhesive member therebetween. A detailed description will be given later with reference to fig. 4 to 12.

The display device DD may further comprise one or more functional layers between the display module DM and the foldable window WM. According to an embodiment, the functional layer may be an anti-reflection layer RPL blocking reflection of external light. The anti-reflection layer RPL may be arranged between the input sensing unit ISP and the foldable window WM.

The anti-reflection layer RPL may comprise a retarder and a polarizer. The retarder may be of a film type or a liquid crystal coating type, and includes

A delayer and/or

A delay device. The polarizer may include a stretched synthetic resin film or liquid crystals aligned in a certain alignment. The retarder and the polarizer may be implemented using a single polarizing film.

The display device DD may further include a support member SP disposed on a rear surface of the display module DM to support the display module DM. The support member SP may be a metal plate. The support member SP may include a stainless steel plate. The strength of the support member SP may be higher than that of the display module DM.

As shown in fig. 3, the support member SP may have a single-layer shape disposed to commonly overlap or correspond to the first and second non-folding regions NFA1 and NFA2 and the first folding region FA 1. However, the present invention is not limited thereto, and the support member SP may include a plurality of support plates corresponding to the first and second non-folding regions NFA1 and NFA2, respectively, and separated from each other with respect to the first folding region FA 1. Alternatively, a plurality of openings may be defined in the support part SP at the folding area, instead of the support part SP including a plurality of support plates separated from each other at the first folding area FA 1.

Fig. 4 is a cross-sectional view of an embodiment of the foldable window WM shown in fig. 3. The foldable window WM may include a plurality of films and an adhesive layer AD bonding the plurality of films to each other. According to an embodiment, the foldable window WM may comprise a first film FI1, a second film FI2 and an adhesive layer AD. The first film FI1 of the plurality of films is farthest from the display module DM and the second film FI2 of the plurality of films is closest to the display module DM. The first film FI1 is in contact with the upper surface of the adhesive layer AD, and the second film FI2 is in contact with the lower surface of the adhesive layer AD. The first film FI1 may form an outer surface of the foldable window WM, and a front surface of the first film FI1 may be exposed to the outside of the display device DD. Due to the contact, the elements may form an interface between them.

The first film FI1 and the second film FI2 may be optically transparent films. The foldable window WM may be disposed on the display module DM (see fig. 3). Since the foldable window WM includes an optically transparent film, an image IM provided from the display module DM may be provided to the outside of the display device DD by passing through the foldable window WM.

The first film FI1 and the second film FI2 may have a relatively high modulus. In an embodiment, for example, each of the moduli of the first and second films FI1 and FI2 may be about 7 gigapascals (GPa) or greater, such as about 7GPa to about 15 GPa.

The first film FI1 and the second film FI2 (films) have a high modulus value, and deformation of the foldable window WM and damage thereto due to external impact can be reduced or effectively prevented accordingly. In particular, damage to the display module DM due to external impact caused by concentrated pressure on a small area like a PEN (e.g., PEN in fig. 5) may be reduced or effectively prevented by the first and second films FI1 and FI2 (a plurality of films) having a high modulus value. Therefore, the durability and impact resistance of the foldable window WM can be improved. However, when the modulus of the foldable window WM is too high, the flexibility thereof is deteriorated, so that the foldable window WM may be damaged by repeated folding and unfolding.

The first film FI1 and the second film FI2 may be polymer films having high modulus and also being flexible. Each of the first film FI1 and the second film FI2 may include a copolymer. In embodiments, for example, the copolymer may be a polyimide copolymer, a polyamide copolymer, or a polyimide-polyamide copolymer. However, the material of the first film FI1 and the second film FI2 is not limited to the examples described above.

In order to bond the first film FI1 and the second film FI2 to each other, an adhesive layer AD may be disposed therebetween. The adhesive layer AD may be an optically transparent adhesive layer. Accordingly, the image IM passing through the foldable window WM can be visually recognized from the outside of the display device DD without distortion.

The adhesive layer AD may include an ultraviolet curable resin or a thermosetting resin. In an embodiment, for example, the adhesive layer AD may include an epoxy-based resin or a urethane acrylate-based resin. However, the material of the adhesive layer AD is not limited to the above-described example.

The thickness DW (e.g. the total thickness) of the foldable window WM may be about 40 micrometers (μm) to about 100 micrometers (μm). The thickness DW of the foldable window WM may be the sum of the thicknesses of the plurality of films and the at least one adhesive layer within the foldable window WM. As shown in fig. 4, the thickness DW of the foldable window WM may be the sum of the first thickness D1 of the first film FI1, the second thickness D2 of the second film FI2, and the third thickness D3 of the adhesive layer AD. Each of the first thickness D1, the second thickness D2, and the third thickness D3 may be a maximum thickness of the respective layer, but is not limited thereto.

When the thickness DW of the foldable window WM is too small, external impact may not be sufficiently absorbed, and the structure of the display device DD disposed under the foldable window WM may be damaged. When the thickness DW of the foldable window WM is excessively large, repeated folding and unfolding of the foldable window WM may cause deformation thereof.

Each of the first thickness D1 of the first film FI1 and the second thickness D2 of the second film FI2 may be greater than the third thickness D3 of the adhesive layer AD. In an embodiment, for example, each of the first thickness D1 of the first film FI1 and the second thickness D2 of the second film FI2 may be about 10 μm to about 35 μm. When the thickness of each of the first and second films FI1 and FI2 is too small, external impact may not be sufficiently absorbed, and when the thickness of each thereof is too large, light transmittance may be reduced, and thus color distortion may occur in the image IM provided to the outside of the display device DD through the foldable window WM.

The first film FI1 and the second film FI2 may be identical. In an embodiment, for example, each of the first and second films FI1 and FI2 may comprise the same material and have the same modulus value. However, the present invention is not limited thereto, and even if the first and second films FI1 and FI2 include the same material, they may have different modulus values, even if the first and second films FI1 and FI2 include the same modulus value, they may include materials different from each other, or both the materials and the moduli thereof may be different from each other.

The third thickness D3 of the adhesive layer AD may be smaller than each of the first thickness D1 of the first film FI1 and the second thickness D2 of the second film FI2, respectively. When the adhesive layer AD has a relatively small thickness, the first film FI1 and the second film FI2 may be thinly adhered. In an embodiment, for example, the third thickness D3 of the adhesive layer AD may be about 1 micrometer (μm) to about 5 micrometers (μm).

When the third thickness D3 of the adhesive layer AD is too small, the first and second films FI1 and FI2 may not be sufficiently joined at room temperature, and when the third thickness D3 of the adhesive layer AD is too large, the first and second films FI1 and FI2 may be peeled by repeated folding and unfolding of the foldable window WM. In addition, when the third thickness D3 of the adhesive layer AD is excessively large, the foldable window WM may be dented or damaged by external impact, especially impact of a sharp object that may extend into the layers of the foldable window WM.

The adhesive layer AD in which the first film FI1 having a modulus of equal to or greater than about 7GPa is joined to the second film FI2 having a modulus of equal to or greater than about 7GPa and which forms an interface with both the first film FI1 and the second film FI2 has adhesive strength. The adhesive strength of the adhesive layer AD may be strong. In an embodiment, for example, the strong adhesive strength of the adhesive layer AD may be about 7 newtons per 20 millimeters (N/20mm) or greater. When the adhesive layer AD has a strong adhesive strength, the first film FI1 and the second film FI2 can strongly adhere despite the continuous folding and unfolding of the foldable window WM.

Fig. 5 is a cross-sectional view showing an embodiment of a pen drop test for the foldable window WM. A PEN drop test can be performed by dropping a PEN of about 5.8 grams onto the collapsible window WM. Through this test, durability and impact resistance can be evaluated by measuring the drop height of the PEN when the foldable window WM is damaged. In particular, the test can evaluate durability and impact resistance against pressure intensively applied to the foldable window WM of a small area. When the foldable window WM does not have sufficient durability and impact resistance, damage may be caused to components (e.g., the display module DM) disposed under the foldable window WM.

Through a PEN drop test performed on the foldable window WM, the drop height of the PEN when the foldable window WM is damaged may be about 10 centimeters (cm) or more. The drop height can be about 10cm to about 30cm, but is not necessarily limited to the above values. Because the films having high modulus are tightly adhered to each other by the thin adhesive layer, one or more embodiments of the foldable window WM can effectively absorb the impact of a sharp object like PEN. Accordingly, damage to the structure or components of the display device DD disposed below the foldable window WM may be reduced or effectively prevented.

Fig. 6 and 7 are sectional views illustrating an embodiment of a process of measuring an inflection angle of the foldable window WM. As shown in fig. 6, the foldable window WM may be foldable about a first folding axis FX1 such that portions of an upper surface of the foldable window WM may face each other.

To measure the deformation angle θ of the foldable window WM (see fig. 7), the foldable window WM is folded as shown in fig. 6 in an environment of humidity of about 93% and a temperature of about 60 degrees celsius (° c) such that the radius of curvature RR is about 1 millimeter (mm). Thereafter, the shape of the foldable window WM is fixed such that the foldable window WM remains folded for a certain period of time, and then the foldable window WM is not fixed and is unfolded, for example, after 24 hours. When unfixed after a period of time, the foldable window WM may be deformed into a shape folded at an angle, as shown in fig. 7.

Referring to fig. 7, the deformation angle θ refers to an outer angle formed by a surface parallel to the first non-folding region NFA1 and a surface parallel to the second non-folding region NFA 2. When the deformation angle θ is small, the foldable window WM can be more easily restored to its original shape (e.g., unfolded shape). In an embodiment, for example, when the deformation angle θ is about 0 °, it means that the foldable window WM is flat or unfolded. According to an embodiment, the deformation angle θ of the foldable window WM may be equal to or less than about 90 degrees (°). The deformation angle theta thereof may be about 40 deg. to about 90 deg., but is not limited to the above values.

The following table shows values of modulus, deformation angle, indentation hardness, light defect and pen drop height for comparative examples and embodiments of the foldable window WM. The "deformation angle" is a deformation angle θ (see fig. 7) measured by the deformation angle measurement test described above. The "indentation hardness" is a value measured by applying pressure to an area with an indentation body. The "bright defect" is a measurement of the height at which the bright defect occurs when approximately 5.8 grams of PEN is dropped into the corresponding foldable window according to the comparative example and the example embodiment. The "pen drop height" is the pen drop height PD measured by the pen drop test described above (see fig. 5).

Comparative examples 1 to 3 of table 1 below are respective foldable windows composed of a film including a single layer of a polyimide-based polymer. Example 1 is a corresponding foldable window having the configuration of the foldable window WM shown in fig. 4 and consisting of a first film FI1 and a second film FI2 comprising a polyamide-based copolymer.

[ Table 1]

Classification	Comparative example 1	Comparative example 2	Comparative example 3	Examples example 1
					Modulus (GPa)	7.1	6.6	7.6	12.0
Deflection angle (°)	128	120	98	90
					Indentation Hardness (HV)	35	45	49	112
Bright defect (cm)	0	0	0	1
					Height of pen falling (cm)	5	5	5	20

Referring to table 1, it can be seen that comparative examples 1 to 3 have a modulus of about 7 GPa. In contrast, it can be seen that example 1 has a relatively high modulus of about 12 GPa.

The deformation angles of comparative examples 1 to 3 were greater than about 90 °. That is, it can be seen that the respective foldable windows of comparative examples 1 to 3 are deformed into a folded shape of less than 90 ° as compared to full unfolding when an external force fixing the respective foldable windows to be folded is removed. In contrast, it can be seen that the respective deformation angles of embodiment example 1 have relatively low values. That is, it can be seen that the foldable window WM of embodiment example 1 has a stronger property of returning to the original shape than the foldable window of the comparative example.

Indentation hardness (in vickers hardness HV) is the value of the hardness of the corresponding foldable window against local loads. It can be seen that although the indentation hardness of each of comparative examples 1 to 3 has a value of about 30 to about 50, the indentation hardness of example 1 is 112, which is relatively very high. From this result, it can be seen that embodiment example 1 can reduce or effectively prevent damage, which is more effective than the comparative example, when a strong pressure is applied to a small area.

The bright defect refers to a spot that appears as a white spot on the corresponding display device because the circuit elements included in the corresponding display panel are damaged by external impact. The value of the light defect listed in table 1 is a drop height of a PEN in which the light defect occurs when about 5.8 g of PEN is dropped on the corresponding display device having the corresponding foldable window including the comparative example and the example. It can be seen that the pen drop height PD of example 1, at which the bright defect occurs, is about 1cm, which is greater than that of the comparative example. From this result, it can be seen that embodiment example 1 can reduce or effectively prevent the corresponding display panel from being damaged, which is more effective than the comparative example.

The PEN drop height PD refers to the drop height value when the corresponding collapsible window is damaged by dropping about 5.8 grams of PEN. It was confirmed that the drop height value of the comparative example was 5cm, while the drop height value of the example 1 was improved by 15cm to 20 cm. From this result, it can be seen that the durability and impact resistance of example 1 are improved when compared with those of the comparative example.

From the values listed in table 1, it can be seen that one or more embodiments of foldable window WM has relatively increased values of indentation hardness, drop height for pen drop test, and pen drop height PD when bright defects occur. In addition, it can also be seen that the deformation angle θ is reduced. From this result, it can be seen that durability and impact resistance against external impact can be improved, strong impact to a small region can be effectively absorbed, and deformation can be more easily returned to an original shape (e.g., flat or unfolded) by adhering a plurality of high modulus films to a thin adhesive layer.

Fig. 8 illustrates an example of a stress-strain graph of a film of a foldable window. Specifically, fig. 8 is a graph showing strain (in percent) versus stress (in megapascals, MPa) of a film. The graph shows the strain versus stress of the film comprising the polyamide-based copolymer. The modulus of the film has a value of 10GPa or greater. The film corresponds to an example of the first film FI1 or the second film FI2 as a component of one or more embodiments of the foldable window WM.

Referring to fig. 8, the hatched area under the curve indicates the toughness of the film. The toughness of a film can be expressed as the amount of energy per unit volume before the film breaks. Because the film according to one or more embodiments of the present invention has high toughness, the film is not easily broken even if the elastic limit is exceeded. Accordingly, components of the display device DD disposed under the foldable window WM may be effectively protected from external impacts.

Fig. 9 to 12 are sectional views showing another embodiment of the foldable window WM of fig. 3. Hereinafter, additional components added to the foldable window WM will be described with reference to fig. 9 to 12.

Referring to fig. 9, the foldable window WM-a may further include a third film FI3 disposed under the second film FI 2. The third film FI3 may be bonded to the lower surface of the second film FI2 by an adhesive layer AD. The third film FI3 faces the first film FI1, while the second film FI2 is located between them. The description given above for the first film FI1 and the second film FI2 can equally be applied to the third film FI 3. The description of the adhesive layer AD given with reference to fig. 4 may be equally applied to an adhesive layer AD joining the third film FI3 and the second film FI2 to each other.

As an example, the first film FI1 to the second film FI2 or the first film FI1 to the second film FI2 and the third film FI3 are shown to be stacked, but the foldable window WM is not limited thereto, and may have a structure in which three or more films are stacked. In an embodiment, for example, the foldable window WM may comprise a third film FI3, the third film FI3 facing the adhesive layer AD with the first film FI1 in between and/or facing the adhesive layer AD with the second film FI2 in between.

Referring to fig. 10, the foldable window WM-b may further include a hard coating layer HC disposed on the first film FI 1. The hard coating layer HC may form an outer surface of the foldable window WM-b and/or a front surface of the display device DD.

The hard coating layer HC may include a hard strength material. The hard coating layer HC may protect the first film FI1 disposed below and may improve the overall strength and impact resistance of the foldable window WM-b. The hard coating HC may define the impact resistant layer of the foldable window WM-b. The hard coating layer HC may include a high-strength material having a pencil hardness of F or more. In an embodiment, for example, the hard coating layer HC may include a silicone resin, an epoxy resin, an acrylic resin, or the like. However, the material of the hard coat layer HC is not limited to the above example.

The hard coating layer HC may additionally comprise a water-or oil-repellent substance. Accordingly, the contamination resistance of the hard coating layer HC may be improved, and the contamination of the surface thereof exposed to the outside of the display device DD may be reduced or effectively prevented. For example, in embodiments, fluorine-based polytetrafluoroethylene ("PTFE"), polyvinylidene fluoride ("PVDF"), amorphous polymers or amorphous fluoroplastics (e.g., Teflon @)

) And fluoropolymers (e.g., Cytop)^TM) Etc. as water-or oil-repellent substances. However, the water-or oil-repellent substance is not limited to the above examples. The hard coating HC may define the liquid-proof layer of the foldable window WM-b.

Referring to fig. 11, foldable window WM-c may include an inorganic layer 101. The inorganic layer 101 may be in contact with the upper surface of the first film FI1 to form an interface therebetween, and be separated from the adhesive layer AD with the first film FI1 therebetween. The inorganic layer 101 may be disposed or formed on the first film FI1, for example, by deposition.

The inorganic layer 101 may protect a plurality of films into which moisture can more easily permeate than the inorganic layer 101. Accordingly, moisture penetration into and under the foldable window WM can be reduced or effectively prevented. The inorganic layer 101 may define a moisture barrier of the foldable window WM-c.

Foldable window WM-c further comprising inorganic layer 101 has moisture vapor transmission rate. Here, the moisture vapor transmission rate is the amount of water vapor that passes through a substance or material in a specific period of time. The moisture vapor transmission rate of foldable window WM-c including inorganic layer 101 may further have a small value. In an embodiment, for example, the moisture vapor transmission rate of one embodiment of foldable window WM-c may be about 0.01 grams per square meter per day (g/m)²Day) to about 10 grams per square meter per day (g/m)²Day).

The thickness of the inorganic layer 101 taken along the third direction DR3 may be about 5 angstroms

To about

When the thickness of the inorganic layer 101 is too small, the effect of preventing moisture permeation may not be sufficiently exhibited. When the thickness of the inorganic layer 101 is excessively large, the brittleness thereof becomes high, the flexibility is reduced, and thus cracks may be caused at the time of folding.

Although not shown, the inorganic layer 101 included in the foldable window WM-c may be disposed in contact with the lower surface of the second film FI2, thereby forming an interface therebetween. In this case, the inorganic layer 101 may be separated from the adhesive layer AD with the second film FI2 therebetween. The inorganic layer 101 included in the foldable window WM-c may be provided in plurality, and the inorganic layers may be provided on the upper surface of the first film FI1 and the lower surface of the second film FI2, respectively. That is, the foldable window WM may comprise an inorganic layer 101, the inorganic layer 101 facing the adhesive layer AD with the first film FI1 located between them and the inorganic layer 101 forming an interface with the first film FI1, and/or the inorganic layer 101 facing the adhesive layer AD with the second film FI2 located between them and the inorganic layer 101 forming an interface with the second film FI 2.

Referring to fig. 12, the foldable window WM-d may further include a hard coating layer HC and an inorganic layer 101. The inorganic layer 101 may be in contact with an upper surface of the first film FI1 to form an interface therebetween, and a hard coating layer HC may be disposed on the inorganic layer 101 to form an interface therebetween. Since the hard coating layer HC is disposed on top of the foldable window WM, structures and layers disposed under the hard coating layer HC may be protected. The description given above with reference to fig. 10 and 11 can be equally applied to the description of the hard coat layer HC and the inorganic layer 101 included in the foldable window WM-d of fig. 12.

Fig. 13 is a sectional view showing an embodiment of the module DM. The display module DM may include a display panel DP and an input sensing unit ISP. The input sensing unit ISP may be disposed on the display panel DP. The description of the input sensing unit ISP given with reference to fig. 3 may equally be applied to the description of the input sensing unit ISP.

The display panel DP may include a substrate SUB, a circuit layer CL, a light emitting element layer EML, and an encapsulation layer TFE. The display panel DP may generate an image IM (see fig. 1) displayed by the display device DD.

The substrate SUB may include a plastic substrate, an organic substrate, a metal substrate, an organic/inorganic composite substrate, or the like. The substrate SUB may include a synthetic resin film, and have not only a single layer of the synthetic resin film but also a multi-layer structure. In the embodiment, for example, the synthetic resin film may include a polyimide-based material, an acrylic-based material, a vinyl-based material, an epoxy-based material, a urethane-based material, a cellulose-based material, or a perylene-based material, but the material of the synthetic resin film is not limited to the above examples.

The circuit layer CL may be disposed on the substrate SUB. The circuit layer CL may include an insulating layer, a semiconductor pattern, a conductive pattern, a signal line, and the like. The circuit layer CL may include a plurality of transistors including a semiconductor pattern, a conductive pattern, a signal line, and the like. In the embodiment, for example, a switching transistor and a driving transistor for driving a light emitting element of the light emitting element layer EML provided on the circuit layer CL may be included in the circuit layer CL.

The light emitting element layer EML may be disposed on the circuit layer CL. The light emitting element layer EML may be disposed to correspond to an active area AA of the display module DM (see fig. 3). The light emitting element layer EML may include a display element such as a light emitting element. In an embodiment, for example, the light emitting element layer EML may include an organic light emitting material, quantum dots, quantum rods, micro light emitting diode ("LED") elements, or nano LED elements.

The encapsulation layer TFE may be disposed on the circuit layer CL to cover the light emitting element layer EML. The encapsulation layer TFE may include inorganic layers and organic layers disposed between the inorganic layers, but the layer forming the encapsulation layer TFE is not limited thereto. The inorganic layer may protect pixels and their elements within the display panel DP from moisture and/or oxygen. The organic layer may protect the pixels from foreign substances such as dust particles. In an embodiment, for example, the inorganic layer may include a silicon nitride layer, a silicon oxide layer, a silicon oxynitride layer, a titanium oxide layer, an aluminum oxide layer, or the like. However, the materials of the inorganic layer and the organic layer are not limited to the above examples.

The input sensing unit ISP may be disposed on the display panel DP. The input sensing unit ISP may comprise a plurality of insulating layers and a plurality of conductive layers. The plurality of conductive layers may include a sensing electrode for sensing an external input TC, a sensing line connected to the sensing electrode, and a sensing pad connected to the sensing line.

Since one or more embodiments of the foldable window WM includes a plurality of films having high modulus and joined by an adhesive layer having strong adhesive strength, durability and impact resistance thereof can be improved. In particular, the impact resistance against external impact exerted on a small area by strong pressure can be improved.

Since one or more embodiments of the display device DD include the foldable window WM having improved durability and impact resistance, the display module DM disposed under the foldable window WM may be effectively protected and the impact resistance of the display device DD may be improved.

According to the embodiment, the foldable window WM and the display device DD including the same have the effect of improving durability and impact resistance.

Although the description has been made above with reference to the embodiments, it will be understood by those skilled in the art or ordinary skill in the art that various modifications and changes may be made to the present invention without departing from the spirit and scope of the technical field of the present invention described in the scope of claims to be described later.

Therefore, the technical scope of the present invention should not be limited to what is described in the detailed description of the specification, but should be determined by the scope of the claims described below.

Claims

1. A foldable window of a display device, the foldable window comprising:

a first film having a modulus;

a second film facing the first film, closer to a display panel of the display device than the first film, and having a modulus; and

an adhesive layer between the first film and the second film joining the first film to the second film,

wherein the modulus of the first film and the modulus of the second film are both equal to or greater than 7 gigapascals.

2. The foldable window of claim 1, wherein each of the first and second films comprises a polyimide copolymer, a polyamide copolymer, or a polyimide-polyamide copolymer.

3. The foldable window of claim 1, wherein each of the first and second films has a thickness, and

the thickness of the first film and the thickness of the second film are both equal to or greater than 10 micrometers and equal to or less than 35 micrometers.

4. The foldable window of claim 1, wherein the modulus of the first film and the modulus of the second film are both equal to or greater than 7 gigapascals and equal to or less than 15 gigapascals.

5. The foldable window of claim 1, wherein,

the adhesive layer joining the first film to the second film has a thickness, and

the thickness of the adhesive layer is equal to or greater than 1 micrometer and equal to or less than 5 micrometers.

6. The foldable window of claim 1, wherein,

the adhesive layer that joins the first film to the second film and forms an interface with both the first film and the second film has adhesive strength, and

the adhesive strength of the adhesive layer is equal to or greater than 7 newtons per 20 millimeters.

7. The foldable window of claim 1, wherein the adhesive layer joining the first film to the second film comprises an epoxy-based resin or a urethane acrylate-based resin.

8. The foldable window of claim 1, wherein the foldable window further comprises an impact resistant layer facing the adhesive layer with the first film between the impact resistant layer and the adhesive layer, and

wherein the impact resistant layer comprises a water or oil repellent material.

9. The foldable window of claim 1, wherein the foldable window further comprises an inorganic layer facing the adhesive layer with the first film between the inorganic layer and the adhesive layer and forming an interface with the first film, or the inorganic layer facing the adhesive layer with the second film between them and forming an interface with the second film.

10. The foldable window of claim 9, wherein the inorganic layer has a thickness, and

the thickness of the inorganic layer is equal to or greater than 5 angstroms and equal to or less than 500 angstroms.